Advance File PhotoDemocrat Mike Ryan is running against Republican Dan Donovan for the District Attorney's office.

STATEN ISLAND, N.Y. -- The race between GOP District Attorney Daniel Donovan and Democratic challenger Michael Ryan is the only contested race on Staten Island today.

It's also the highest profile contested race in all of New York City.

So how come the campaigns don't expect very many voters to come out?

Those working on both sides of the race expect between 25,000 and 30,000 voters will go to the polls today. At the high end, that would be little more than 10 percent of the borough's 268,181 registered voters.

"That's abysmal," said Island political consultant Vincent Montalbano, a Democrat who is not working for either campaign. "I can't imagine it getting lower than that."

Montalbano said the biggest reason for the expected low turnout is the fact that the D.A.'s race here usually falls during an "off-year," when there are no state- or citywide races on the ballot to drum up additional interest.

"Sticking an election like this out there all alone has got to just drive down turnout," he said.

Much the same will be seen in the other boroughs today, where there are only a handful of competitive judicial races on the ballot. Two other D.A.s, Robert Johnson in the Bronx and Richard Brown of Queens, are running unopposed.

In 2007, close to 30,000 voters came out when Donovan beat Ryan. Donovan may have gotten a boost that year with Republican City Councilman Vincent Ignizio also running on the South Shore.

In 2003, more than 48,000 voted when Donovan beat Democrat David Lehr, but there were also three Council races on the ballot that year, as well as a non-partisan elections ballot question.

Montalbano suggested moving the D.A.'s race to a busier year, such as when presidential, gubernatorial or mayoral elections are on the ballot.

National, statewide and citywide elections always goose the turnout, Montalbano said, meaning that more attention would be paid to the D.A.'s races if they shared the ballot.

But there's another reason that voters don't pay attention to D.A. races, Montalbano said: Few ever picture themselves being the victim or the perpetrator of a crime, so they tend to give little thought to the criminal justice system.

"People have much more contact with the legislative and executive branches," he said.

Knowing the turnout will be small, both campaigns have worked to identify "prime" voters (voters who vote in every election), and alert them to the race. Then it's a matter of pulling them out.

The GOP was long the champ of low-turnout elections. But the Dems have improved their organization over the last few years, and registered Democrats still outnumber Republicans by about 5-to-3 here.

That being said, Donovan beat Ryan with 68 percent of the vote in 2007, meaning that a lot of Democrats voted for him. The same goes for 2010, when 65 percent of Islanders voted for Donovan in his failed bid for attorney general.

One wild card could boost turnout: The weather.

Temperatures are expected to be close to 70 degrees today, with no rain expected. That could entice more people out to vote.

Ryan yesterday was endorsed by former city Comptroller and 2009 mayoral candidate William Thompson, and by the Council of School Supervisors and Administrators. He has also been backed by the Conservative Party.

Donovan, who is also endorsed by the Independence Party, yesterday tended to official D.A. office business.

GOP Judge Joseph Maltese is also running unopposed for state Supreme Court today.